1 /*
2 * ASN.1 buffer writing functionality
3 *
4 * Copyright The Mbed TLS Contributors
5 * SPDX-License-Identifier: Apache-2.0
6 *
7 * Licensed under the Apache License, Version 2.0 (the "License"); you may
8 * not use this file except in compliance with the License.
9 * You may obtain a copy of the License at
10 *
11 * http://www.apache.org/licenses/LICENSE-2.0
12 *
13 * Unless required by applicable law or agreed to in writing, software
14 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
15 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
16 * See the License for the specific language governing permissions and
17 * limitations under the License.
18 */
19
20 #include "common.h"
21
22 #if defined(MBEDTLS_ASN1_WRITE_C)
23
24 #include "mbedtls/asn1write.h"
25 #include "mbedtls/error.h"
26
27 #include <string.h>
28
29 #if defined(MBEDTLS_PLATFORM_C)
30 #include "mbedtls/platform.h"
31 #else
32 #include <stdlib.h>
33 #define mbedtls_calloc calloc
34 #define mbedtls_free free
35 #endif
36
mbedtls_asn1_write_len(unsigned char ** p,const unsigned char * start,size_t len)37 int mbedtls_asn1_write_len( unsigned char **p, const unsigned char *start, size_t len )
38 {
39 if( len < 0x80 )
40 {
41 if( *p - start < 1 )
42 return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
43
44 *--(*p) = (unsigned char) len;
45 return( 1 );
46 }
47
48 if( len <= 0xFF )
49 {
50 if( *p - start < 2 )
51 return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
52
53 *--(*p) = (unsigned char) len;
54 *--(*p) = 0x81;
55 return( 2 );
56 }
57
58 if( len <= 0xFFFF )
59 {
60 if( *p - start < 3 )
61 return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
62
63 *--(*p) = MBEDTLS_BYTE_0( len );
64 *--(*p) = MBEDTLS_BYTE_1( len );
65 *--(*p) = 0x82;
66 return( 3 );
67 }
68
69 if( len <= 0xFFFFFF )
70 {
71 if( *p - start < 4 )
72 return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
73
74 *--(*p) = MBEDTLS_BYTE_0( len );
75 *--(*p) = MBEDTLS_BYTE_1( len );
76 *--(*p) = MBEDTLS_BYTE_2( len );
77 *--(*p) = 0x83;
78 return( 4 );
79 }
80
81 #if SIZE_MAX > 0xFFFFFFFF
82 if( len <= 0xFFFFFFFF )
83 #endif
84 {
85 if( *p - start < 5 )
86 return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
87
88 *--(*p) = MBEDTLS_BYTE_0( len );
89 *--(*p) = MBEDTLS_BYTE_1( len );
90 *--(*p) = MBEDTLS_BYTE_2( len );
91 *--(*p) = MBEDTLS_BYTE_3( len );
92 *--(*p) = 0x84;
93 return( 5 );
94 }
95
96 #if SIZE_MAX > 0xFFFFFFFF
97 return( MBEDTLS_ERR_ASN1_INVALID_LENGTH );
98 #endif
99 }
100
mbedtls_asn1_write_tag(unsigned char ** p,const unsigned char * start,unsigned char tag)101 int mbedtls_asn1_write_tag( unsigned char **p, const unsigned char *start, unsigned char tag )
102 {
103 if( *p - start < 1 )
104 return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
105
106 *--(*p) = tag;
107
108 return( 1 );
109 }
110
mbedtls_asn1_write_raw_buffer(unsigned char ** p,const unsigned char * start,const unsigned char * buf,size_t size)111 int mbedtls_asn1_write_raw_buffer( unsigned char **p, const unsigned char *start,
112 const unsigned char *buf, size_t size )
113 {
114 size_t len = 0;
115
116 if( *p < start || (size_t)( *p - start ) < size )
117 return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
118
119 len = size;
120 (*p) -= len;
121 memcpy( *p, buf, len );
122
123 return( (int) len );
124 }
125
126 #if defined(MBEDTLS_BIGNUM_C)
mbedtls_asn1_write_mpi(unsigned char ** p,const unsigned char * start,const mbedtls_mpi * X)127 int mbedtls_asn1_write_mpi( unsigned char **p, const unsigned char *start, const mbedtls_mpi *X )
128 {
129 int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
130 size_t len = 0;
131
132 // Write the MPI
133 //
134 len = mbedtls_mpi_size( X );
135
136 if( *p < start || (size_t)( *p - start ) < len )
137 return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
138
139 (*p) -= len;
140 MBEDTLS_MPI_CHK( mbedtls_mpi_write_binary( X, *p, len ) );
141
142 // DER format assumes 2s complement for numbers, so the leftmost bit
143 // should be 0 for positive numbers and 1 for negative numbers.
144 //
145 if( X->s ==1 && **p & 0x80 )
146 {
147 if( *p - start < 1 )
148 return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
149
150 *--(*p) = 0x00;
151 len += 1;
152 }
153
154 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, len ) );
155 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start, MBEDTLS_ASN1_INTEGER ) );
156
157 ret = (int) len;
158
159 cleanup:
160 return( ret );
161 }
162 #endif /* MBEDTLS_BIGNUM_C */
163
mbedtls_asn1_write_null(unsigned char ** p,const unsigned char * start)164 int mbedtls_asn1_write_null( unsigned char **p, const unsigned char *start )
165 {
166 int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
167 size_t len = 0;
168
169 // Write NULL
170 //
171 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, 0) );
172 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start, MBEDTLS_ASN1_NULL ) );
173
174 return( (int) len );
175 }
176
mbedtls_asn1_write_oid(unsigned char ** p,const unsigned char * start,const char * oid,size_t oid_len)177 int mbedtls_asn1_write_oid( unsigned char **p, const unsigned char *start,
178 const char *oid, size_t oid_len )
179 {
180 int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
181 size_t len = 0;
182
183 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_raw_buffer( p, start,
184 (const unsigned char *) oid, oid_len ) );
185 MBEDTLS_ASN1_CHK_ADD( len , mbedtls_asn1_write_len( p, start, len ) );
186 MBEDTLS_ASN1_CHK_ADD( len , mbedtls_asn1_write_tag( p, start, MBEDTLS_ASN1_OID ) );
187
188 return( (int) len );
189 }
190
mbedtls_asn1_write_algorithm_identifier(unsigned char ** p,const unsigned char * start,const char * oid,size_t oid_len,size_t par_len)191 int mbedtls_asn1_write_algorithm_identifier( unsigned char **p, const unsigned char *start,
192 const char *oid, size_t oid_len,
193 size_t par_len )
194 {
195 int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
196 size_t len = 0;
197
198 if( par_len == 0 )
199 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_null( p, start ) );
200 else
201 len += par_len;
202
203 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_oid( p, start, oid, oid_len ) );
204
205 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, len ) );
206 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start,
207 MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE ) );
208
209 return( (int) len );
210 }
211
mbedtls_asn1_write_bool(unsigned char ** p,const unsigned char * start,int boolean)212 int mbedtls_asn1_write_bool( unsigned char **p, const unsigned char *start, int boolean )
213 {
214 int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
215 size_t len = 0;
216
217 if( *p - start < 1 )
218 return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
219
220 *--(*p) = (boolean) ? 255 : 0;
221 len++;
222
223 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, len ) );
224 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start, MBEDTLS_ASN1_BOOLEAN ) );
225
226 return( (int) len );
227 }
228
asn1_write_tagged_int(unsigned char ** p,const unsigned char * start,int val,int tag)229 static int asn1_write_tagged_int( unsigned char **p, const unsigned char *start, int val, int tag )
230 {
231 int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
232 size_t len = 0;
233
234 do
235 {
236 if( *p - start < 1 )
237 return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
238 len += 1;
239 *--(*p) = val & 0xff;
240 val >>= 8;
241 }
242 while( val > 0 );
243
244 if( **p & 0x80 )
245 {
246 if( *p - start < 1 )
247 return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
248 *--(*p) = 0x00;
249 len += 1;
250 }
251
252 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, len ) );
253 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start, tag ) );
254
255 return( (int) len );
256 }
257
mbedtls_asn1_write_int(unsigned char ** p,const unsigned char * start,int val)258 int mbedtls_asn1_write_int( unsigned char **p, const unsigned char *start, int val )
259 {
260 return( asn1_write_tagged_int( p, start, val, MBEDTLS_ASN1_INTEGER ) );
261 }
262
mbedtls_asn1_write_enum(unsigned char ** p,const unsigned char * start,int val)263 int mbedtls_asn1_write_enum( unsigned char **p, const unsigned char *start, int val )
264 {
265 return( asn1_write_tagged_int( p, start, val, MBEDTLS_ASN1_ENUMERATED ) );
266 }
267
mbedtls_asn1_write_tagged_string(unsigned char ** p,const unsigned char * start,int tag,const char * text,size_t text_len)268 int mbedtls_asn1_write_tagged_string( unsigned char **p, const unsigned char *start, int tag,
269 const char *text, size_t text_len )
270 {
271 int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
272 size_t len = 0;
273
274 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_raw_buffer( p, start,
275 (const unsigned char *) text, text_len ) );
276
277 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, len ) );
278 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start, tag ) );
279
280 return( (int) len );
281 }
282
mbedtls_asn1_write_utf8_string(unsigned char ** p,const unsigned char * start,const char * text,size_t text_len)283 int mbedtls_asn1_write_utf8_string( unsigned char **p, const unsigned char *start,
284 const char *text, size_t text_len )
285 {
286 return( mbedtls_asn1_write_tagged_string(p, start, MBEDTLS_ASN1_UTF8_STRING, text, text_len) );
287 }
288
mbedtls_asn1_write_printable_string(unsigned char ** p,const unsigned char * start,const char * text,size_t text_len)289 int mbedtls_asn1_write_printable_string( unsigned char **p, const unsigned char *start,
290 const char *text, size_t text_len )
291 {
292 return( mbedtls_asn1_write_tagged_string(p, start, MBEDTLS_ASN1_PRINTABLE_STRING, text, text_len) );
293 }
294
mbedtls_asn1_write_ia5_string(unsigned char ** p,const unsigned char * start,const char * text,size_t text_len)295 int mbedtls_asn1_write_ia5_string( unsigned char **p, const unsigned char *start,
296 const char *text, size_t text_len )
297 {
298 return( mbedtls_asn1_write_tagged_string(p, start, MBEDTLS_ASN1_IA5_STRING, text, text_len) );
299 }
300
mbedtls_asn1_write_named_bitstring(unsigned char ** p,const unsigned char * start,const unsigned char * buf,size_t bits)301 int mbedtls_asn1_write_named_bitstring( unsigned char **p,
302 const unsigned char *start,
303 const unsigned char *buf,
304 size_t bits )
305 {
306 size_t unused_bits, byte_len;
307 const unsigned char *cur_byte;
308 unsigned char cur_byte_shifted;
309 unsigned char bit;
310
311 byte_len = ( bits + 7 ) / 8;
312 unused_bits = ( byte_len * 8 ) - bits;
313
314 /*
315 * Named bitstrings require that trailing 0s are excluded in the encoding
316 * of the bitstring. Trailing 0s are considered part of the 'unused' bits
317 * when encoding this value in the first content octet
318 */
319 if( bits != 0 )
320 {
321 cur_byte = buf + byte_len - 1;
322 cur_byte_shifted = *cur_byte >> unused_bits;
323
324 for( ; ; )
325 {
326 bit = cur_byte_shifted & 0x1;
327 cur_byte_shifted >>= 1;
328
329 if( bit != 0 )
330 break;
331
332 bits--;
333 if( bits == 0 )
334 break;
335
336 if( bits % 8 == 0 )
337 cur_byte_shifted = *--cur_byte;
338 }
339 }
340
341 return( mbedtls_asn1_write_bitstring( p, start, buf, bits ) );
342 }
343
mbedtls_asn1_write_bitstring(unsigned char ** p,const unsigned char * start,const unsigned char * buf,size_t bits)344 int mbedtls_asn1_write_bitstring( unsigned char **p, const unsigned char *start,
345 const unsigned char *buf, size_t bits )
346 {
347 int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
348 size_t len = 0;
349 size_t unused_bits, byte_len;
350
351 byte_len = ( bits + 7 ) / 8;
352 unused_bits = ( byte_len * 8 ) - bits;
353
354 if( *p < start || (size_t)( *p - start ) < byte_len + 1 )
355 return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
356
357 len = byte_len + 1;
358
359 /* Write the bitstring. Ensure the unused bits are zeroed */
360 if( byte_len > 0 )
361 {
362 byte_len--;
363 *--( *p ) = buf[byte_len] & ~( ( 0x1 << unused_bits ) - 1 );
364 ( *p ) -= byte_len;
365 memcpy( *p, buf, byte_len );
366 }
367
368 /* Write unused bits */
369 *--( *p ) = (unsigned char)unused_bits;
370
371 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, len ) );
372 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start, MBEDTLS_ASN1_BIT_STRING ) );
373
374 return( (int) len );
375 }
376
mbedtls_asn1_write_octet_string(unsigned char ** p,const unsigned char * start,const unsigned char * buf,size_t size)377 int mbedtls_asn1_write_octet_string( unsigned char **p, const unsigned char *start,
378 const unsigned char *buf, size_t size )
379 {
380 int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
381 size_t len = 0;
382
383 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_raw_buffer( p, start, buf, size ) );
384
385 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, len ) );
386 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start, MBEDTLS_ASN1_OCTET_STRING ) );
387
388 return( (int) len );
389 }
390
391
392 /* This is a copy of the ASN.1 parsing function mbedtls_asn1_find_named_data(),
393 * which is replicated to avoid a dependency ASN1_WRITE_C on ASN1_PARSE_C. */
asn1_find_named_data(mbedtls_asn1_named_data * list,const char * oid,size_t len)394 static mbedtls_asn1_named_data *asn1_find_named_data(
395 mbedtls_asn1_named_data *list,
396 const char *oid, size_t len )
397 {
398 while( list != NULL )
399 {
400 if( list->oid.len == len &&
401 memcmp( list->oid.p, oid, len ) == 0 )
402 {
403 break;
404 }
405
406 list = list->next;
407 }
408
409 return( list );
410 }
411
mbedtls_asn1_store_named_data(mbedtls_asn1_named_data ** head,const char * oid,size_t oid_len,const unsigned char * val,size_t val_len)412 mbedtls_asn1_named_data *mbedtls_asn1_store_named_data(
413 mbedtls_asn1_named_data **head,
414 const char *oid, size_t oid_len,
415 const unsigned char *val,
416 size_t val_len )
417 {
418 mbedtls_asn1_named_data *cur;
419
420 if( ( cur = asn1_find_named_data( *head, oid, oid_len ) ) == NULL )
421 {
422 // Add new entry if not present yet based on OID
423 //
424 cur = (mbedtls_asn1_named_data*)mbedtls_calloc( 1,
425 sizeof(mbedtls_asn1_named_data) );
426 if( cur == NULL )
427 return( NULL );
428
429 cur->oid.len = oid_len;
430 cur->oid.p = mbedtls_calloc( 1, oid_len );
431 if( cur->oid.p == NULL )
432 {
433 mbedtls_free( cur );
434 return( NULL );
435 }
436
437 memcpy( cur->oid.p, oid, oid_len );
438
439 cur->val.len = val_len;
440 if( val_len != 0 )
441 {
442 cur->val.p = mbedtls_calloc( 1, val_len );
443 if( cur->val.p == NULL )
444 {
445 mbedtls_free( cur->oid.p );
446 mbedtls_free( cur );
447 return( NULL );
448 }
449 }
450
451 cur->next = *head;
452 *head = cur;
453 }
454 else if( val_len == 0 )
455 {
456 mbedtls_free( cur->val.p );
457 cur->val.p = NULL;
458 }
459 else if( cur->val.len != val_len )
460 {
461 /*
462 * Enlarge existing value buffer if needed
463 * Preserve old data until the allocation succeeded, to leave list in
464 * a consistent state in case allocation fails.
465 */
466 void *p = mbedtls_calloc( 1, val_len );
467 if( p == NULL )
468 return( NULL );
469
470 mbedtls_free( cur->val.p );
471 cur->val.p = p;
472 cur->val.len = val_len;
473 }
474
475 if( val != NULL )
476 memcpy( cur->val.p, val, val_len );
477
478 return( cur );
479 }
480 #endif /* MBEDTLS_ASN1_WRITE_C */
481